Blade constructs and methods of forming blade constructs

ABSTRACT

A dual-core blade and method for manufacturing a dual-core blade are disclosed. The blade is formed with a first core portion and a second core portion comprising an epoxy having a plurality of expanded microspheres. The method of forming the two foams generally comprises sizing a foam core to form a first core portion and providing and preparing an epoxy mixture to form a second core portion. The first core portion and the second core portion of the epoxy mixture are placed into a preform, and the preform is heated slightly so as to cause the epoxy mixture to flow into the shape of the preform and around the first core portion. The first core portion and the second core portion are then bonded in a molding operation. The formed structure can form part of a hockey stick blade.

FIELD OF INVENTION

This invention relates generally to fabrication of molded structures.More particularly, aspects of this invention relate to hockey bladesformed from more than one foam core. The cores can include a foam coreand a core formed from an epoxy having expandable thermoplasticmicrospheres. Types of foam cores that can be used in conjunction withthe various aspects disclosed herein are disclosed in U.S. patentapplication Ser. Nos. 12/048,941, 12/048,976, and 12/469,349, which areall incorporated herein fully by reference.

BACKGROUND

Typical hockey stick blades are generally made of a core reinforced withone or more layers of synthetic materials such as fiberglass, carbonfiber or Aramid. The core of the blade may also be made of a syntheticmaterial reinforced with layers of fibers. The layers may be made of awoven filament fiber, preimpregnated with resin. These structures mayinclude a foam core with a piece of fiber on the front face of the bladeand a second piece of fiber on the rear face of the blade, in the mannerof pieces of bread in a sandwich.

SUMMARY

The following presents a general summary of aspects of the invention inorder to provide a basic understanding of the invention and variousfeatures of it. This summary is not intended to limit the scope of theinvention in any way, but it simply provides a general overview andcontext for the more detailed description that follows.

Aspects of this invention relate to systems and methods for fabricatinga formed dual-core structure.

In one aspect of the invention, a method for forming a dual-core bladecomprises sizing a foam core to form a first core portion and providingan epoxy mixture to form a second core portion. The first core portionand the second core portion are placed into a preform, and the preformis heated so as to cause the epoxy mixture to flow into the shape of thepreform and around the first core portion. The first core portion andthe second core portion are then wrapped with fiber tape to create awrapped preform. The first core portion is stitched with a thread, andthe thread extends between a first wrapped face and a second wrappedface of the wrapped preform. The wrapped preform is placed in a mold andheated to bond the first core portion and the second core portion. Themold is then cooled and the formed structure is removed from the mold.

In another aspect of the invention, the first core portion is curvedprior to placing the first core portion into the preform.

In another aspect of the invention, the first core portion and thesecond core portion are wrapped with a layer carbon fiber. The layer ofcarbon fiber comprises a first sheet and a second sheet, and the firstcore portion and the second core portion are placed on the first sheet.The first sheet is wrapped around portions of the first core portion andthe second core portion, and the second sheet is placed over the firstcore portion and the second core portion prior to placing the first coreportion and the second core portion into the preform.

In another aspect of the invention, the second core portion mixture cancomprise a plurality of expanded and partially expanded microspheres,and once the mold is heated, the partially expanded microspheres fullyexpand. Alternatively, the second core portion mixture can comprise aplurality of expanded and unexpanded microspheres, and once the mold isheated, the unexpanded microspheres fully expand.

In another aspect of the invention, after wrapping the foam core with alayer of fiber tape, a non-tacky veil is placed on at least a portion ofthe first core portion.

In another aspect of the invention, a blade comprises a first coreportion formed of foam and a second core portion comprising an epoxyhaving a plurality of expanded microspheres. The first core portion andthe second core portion form a core comprising a first core face and asecond core face. A layer of carbon fiber is wrapped around the core anda layer of resin preimpregnated tape is wrapped continuously around atleast the first core face and the second core face. A thread is stitchedon the preimpregnated tape on the first core portion.

In another aspect of the invention, the first core portion and thesecond core portion are bonded to form a continuous core. In particular,the first core portion has a bottom surface which is bonded to a topsurface of the second core portion by cross-linking the epoxy.

In another aspect of the invention, a non adhesive scrim is applied tothe portions of the resin preimpregnated tape that extend along thefirst core portion.

In another aspect of the invention, the core forms part of a hockeyblade comprising a toe region and a heel. The first core portion canhave an oval-shaped end, and the second core portion can also have anoval-shaped end. Additionally, an end of the first core portion or thesecond core portion can have a hook shape to accommodate acorrespondingly shaped oval-shaped end. The first core portion canextend from the heel of the blade to the toe region of the blade, andthe second core portion can extend from the toe region of the blade tothe heel of the blade. The first core portion can be formed thickest atthe heel portion of the blade and taper from the heel of the blade tothe toe region of the blade. The second core portion can be formedthickest at the toe region of the blade and taper from the toe region ofthe blade to the heel of the blade. Additionally, the first core can beof a lower density than second core portion.

Other objects and features of the invention will become apparent byreference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and certainadvantages thereof may be acquired by referring to the followingdetailed description in consideration with the accompanying drawings, inwhich:

FIG. 1 generally illustrates an isometric side view of a core formed inthe shape of a blade;

FIG. 2 generally illustrates an isometric side view of a core formed inthe shape of a blade wrapped with tape;

FIG. 3 is an isometric side view of the core with a cross sectional viewtaken along line 3-3 of FIG. 2;

FIG. 4 is an isometric side view of an alternative embodiment of a coreformed in the shape of a blade;

FIG. 5 is an isometric side view of another alternative embodiment of acore formed in the shape of a blade;

FIG. 6 depicts a manufacturing process of a blade formed in accordancewith one aspect of the invention; and

FIG. 7 illustrates an isometric view of a preform tool used inconjunction with one aspect of the invention.

The reader is advised that the attached drawings are not necessarilydrawn to scale.

DETAILED DESCRIPTION

In the following description of various example structures in accordancewith the invention, reference is made to the accompanying drawings,which form a part hereof, and in which are shown by way of illustrationof various structures in accordance with the invention. Additionally, itis to be understood that other specific arrangements of parts andstructures may be utilized, and structural and functional modificationsmay be made without departing from the scope of the present invention.Also, while the terms “top” and “bottom” and the like may be used inthis specification to describe various example features and elements ofthe invention, these terms are used herein as a matter of convenience,e.g., based on the example orientations shown in the figures and/or theorientations in typical use. Nothing in this specification should beconstrued as requiring a specific three dimensional or spatialorientation of structures in order to fall within the scope of thisinvention.

In general, as described above, aspects of this invention relate tosystems and methods for fabricating a structure, such as a hockey stickblade. More detailed descriptions of aspects of this invention follow.

As shown in FIG. 1, a hockey blade 100 is shown having a toe region 106,a middle region 108 and a heel 110. A core 102 of the hockey blade 100can be formed of a first lower density foam core portion 102A and asecond higher density foam core portion 102B. The first core portion102A can be stitched using a thread 112 (shown in FIG. 2). The secondcore portion 102B can be formed of an epoxy having a plurality ofpolymeric shell microspheres. The first core portion 102A and the secondcore portion 102B are bonded to form the continuous core 102. Inparticular, the first core portion 102A has a bottom surface 104A whichis bonded to a top surface 104B of the second core portion 102B during amolding and cross-linking process.

The first core portion 102A extends from the heel 110 of the blade tothe toe region 106 of the blade. The first core portion 102A can beformed thickest at the heel 110 of the blade and can taper from the heel110 of the blade to the toe region 106 of the blade. Forming the firstcore portion 102A thickest or widest in the heel 110 compensates for theloss of stiffness due to the lower density and lower modulus of thefoam. The second core portion 102B extends from the toe region 106 ofthe blade to the heel 110 of the blade 100. The second core portion canbe thickest at the toe region 106 of the blade 100 and can taper fromthe toe region 106 of the blade 100 to the heel 110 of the blade 100.Both the first core portion 102A and the second core portion 102B canextend all the way to the toe edge 114 of the blade 100. It isunderstood, however, that other arrangements and ratios of the coreportions 102A, 102B can be formed to accomplish different stickcharacteristics, weights, and strengths. For example, the core portionscan be formed in different arrangements as shown in FIGS. 4 and 5, thedescription of which follows.

FIG. 4 shows an alternative arrangement. The blade 400 comprises a firstcore portion 402A and second core portion 402B, which makes up the core402. The arrangement is similar to the arrangement in FIG. 1 with theexception that the first core portion 402A does not extend as far downthe blade 400. In addition, the joint 416 between the first core portion402A and the second core portion 402B forms a straighter line. Thestraight line joint 416 is advantageous as it may reduce the overallstress on the blade during use.

Another alternative arrangement is shown in FIG. 5. The embodiment shownin FIG. 5 is similar to the embodiments shown in FIGS. 1 and 4. However,the core 502 of the blade 500 has first and second core portions 502Aand 502B that are formed with an oval-like shape at one end and a hookshape at the other end to receive the respective oval-like shaped ends.If one of the core portions 502A or 502B is formed with an epoxy, thisarrangement and shaping of the first and second core portions 502A and502B allows for the epoxy to flow and fill more evenly in the formationprocess.

The blade can be manufactured by forming a construct of two foams. Thefirst core portion can be formed of a foam having a low density. Thesecond core portion can be formed with an epoxy having a plurality ofexpanded polymeric shell microspheres. A suitable foam for the firstcore portion is polymethacrylimide (PMI) foam, which is manufacturedunder the name Rohacell. Additionally, a suitable low density PMI foamis RIMA (Resin Infusion Manufacturing Aid) foam. This type of foam is ahigh strength foam that can withstand the shear and impact forces thatresult when a hockey blade strikes a hockey puck. As shown in thevarious embodiments disclosed herein, the foam can be placed on variouslocations of the blade to create a blade with zones of varying density,such as the top or the toe of the blade to reduce weight.

The method of forming the two foams generally comprises sizing a foamcore to form a first core portion and providing and preparing an epoxymixture to form a second core portion. The first core portion and thesecond core portion consisting of the epoxy mixture are placed into apreform, and the preform is heated slightly so as to cause the epoxymixture to flow into the shape of the preform and around the first coreportion.

The first core portion is formed during a first preform process wherethe low density foam is laser cut into the desired 2-D profile from aflat sheet. Then, the cut flat piece of foam is placed into a firstpreform tool (not shown) and heated to approximately 208° C. to form theproper curve of the first core portion.

Next, as shown in FIG. 6, an epoxy material 620 is added adjacent thelow density foam material 622 onto a carbon fiber layer 624. The carbonfiber layer 624 is then wrapped around the edges of the preform, andthen a second carbon fiber layer (not shown) is added to the preform onthe opposite side of the preform so as to cover the first core portionand the second core portion and overlaps the edges of the carbon fiberlayer 624 and may have cut portions to provide for easier wrapping ofthe blade. The carbon fiber layers serve as a release film on thepreform later in the process and aids the manufacturing process as theepoxy material is very sticky and difficult to work with. Additionally,the carbon fiber layers improve the overall structure of the blade whenthe epoxy begins to cross-link and bond.

The wrapped preform consisting of the low density foam material 622, theepoxy material 620, and the carbon fiber are then placed inside a secondpreform tool 700, which is depicted in FIG. 7. The low density foammaterial 622 and the epoxy material 620 respectively form the first coreportion and the second core portion of the blade. In the preform tool700, both the first core portion and the second core portion arepreformed together to create a single dual-density but un-cured preform,and the two different materials of the first and second core portionsare pushed together in the shape of a hockey stick blade core. This isaccomplished by heating the first and second core portions under a lowheat, approximately 20° C. to 40° C. The low heat causes the epoxymaterial to soften and allows it to flow into the shape of the secondpreform tool 700 and around the first core portion. At this point, thesecond core portion can comprise a mixture of expanded, partiallyexpanded, and unexpanded microspheres. In particular, the entire secondcore portion is formed of an epoxy core material which may consist of aplurality of expanded, partially expanded, and unexpanded microspheres.Some of the microspheres are thus expanded by a heating process prior toplacing the epoxy mixture into the mold. However, the unexpandedmicrospheres and partially expanded will not expand until the finalmolding process. The second core portion mixture can also include achopped fiber and a curing agent. The carbon fiber layer allows theformed structure to be easily released from the second preform tool 700.

The structure is then wrapped with carbon fiber tape 22. The carbonfiber tape 22 is preimpregnated with resin. As shown in FIGS. 2 and 3,the core 102 comprises a first core face and a second core face and alayer of resin preimpregnated tape 22 is wrapped continuously around atleast the first core face and the second core face. FIG. 2 illustrates aside view of the core 102 formed in the shape of a blade and wrappedwith tape 22. FIG. 3 is a cross-sectional view taken along line 3-3 ofFIG. 3, which shows the tape 22 wrapped continuously around the core102. The tape 22 is wrapped continuously around the first face surface30, the first edge 32, the second face surface 34 and the second edge36. This continuous wrapping of the preform 20 with the tape 22 resultsin a first wrapped face 40, a second wrapped face 44, a top wrapped edge42 and a bottom wrapped edge 46. The fiber tape 22 can be preimpregnatedwith resin. The thickness of the tape 22 in FIG. 3 is exaggerated forpurposes of more clearly illustrating the invention.

The first preform or core portion 102A and the second preform or coreportion 102B can be wrapped with fiber tape to create a wrapped preform.The preform comprises a first face surface, a second face surface, afirst edge surface and a second edge surface, and the fiber tape can bewrapped continuously around the first face surface, the first edgesurface, the second face surface, and the second edge surface. As shownin FIG. 3, the preform has a first face surface 30, a first edge 32, asecond face surface 34, and a second edge 36.

The tape may be wrapped in various configurations around the core, suchas at a 30 or 45° angle to the longitudinal axis of the blade. A secondlayer of preimpregnated tape may be wrapped at a 90° angle to the tape.

The tape 22 extends around the entire core, to the end of the toe 106,but for purposes of more clearly illustrating aspects of the invention,the tape 22 is not shown extending to the end of the toe 106 of the core102.

The use of tape wrapped continuously around the entire core 102,including the edges, is advantageous over a sandwich configuration,where the tape does not continuously extend of over the edges, forseveral reasons. A hockey blade must be very durable and capable ofwithstanding large forces from a variety of directions. For example, thehockey blade can encounter considerable forces, such as from striking apuck or the surface of the ice in multiple manners and angles. Thus, thecore needs reinforcement in all directions. The wrap configurationresults in a torsionally stiffer and stronger structure. The wrapconfiguration also is better able to withstand shear forces.

It is to be understood that the tape need not consist of a singleunitary piece or sheet of material. For example, the tape can consist ofa combination of multiple pieces or sheets that overlap.

After wrapping the core with a layer of fiber tape, a non-tacky veil canbe placed on at least a portion of the first core portion 102A. Thefirst core portion is then stitched with a polyester thread, and thethread extends between a first wrapped face and a second wrapped face.

A thread 112 in the pattern shown in FIG. 2, is stitched along the layerof preimpregnated tape on the first core portion. The thread can beformed of a high strength polyester, carbon fiber, or a carbon fiberpreimpregnated with resin. A non adhesive scrim can be applied to theportions of the resin preimpregnated tape specifically along the firstcore portion 102A that extend along the first core face and the secondcore face to permit easier stitching of the blade. The non adhesivescrim can be formed from of one of woven fiberglass and polyester.

The stitching is accomplished with an industrial sewing machine (notshown). Placement of the wrapped structure with tape preimpregnated withresin in a sewing machine can cause the machine to stick or jam, and itcan otherwise be difficult to operate the sewing machine with a stickystructure. The veil material described above is not sticky and thusmakes it easier to stitch the wrapped core in the sewing machine.

The thread can extend from the first wrapped face 40 through the core102 to the second wrapped face 44. The thread creates the effect of anI-beam between the first wrapped face 40 and the second wrapped face 44and adds structural and shear strength and rigidity between the faces.If the veil (not shown) were used, it would be positioned along thewrapped faces 40, 44 covering the first core portion and the thread 112would be positioned along the veil.

The thread 112 also pulls the tape toward the first wrapped face 40 andthe second wrapped face 44 at the point where the thread 112 enters thecore 102. The wrapped, stitched core is not flat in that the result ofthe thread 112 pulling the tape 40 toward the core 102 and variouslocations creates a somewhat bumpy or pillow effect on the surface ofthe first wrapped face 40 and the second wrapped face 44. It isunderstood that other stitching patterns and types are contemplated.

The wrapped preform is then placed in a mold, and the mold is thenheated. The mold is heated to an appropriate temperature. In oneembodiment, the mold is heated to 140° C. Upon heating, the epoxysoftens, cross-links, and hardens, and the unexpanded or partiallyexpanded microspheres expand in the epoxy mixture. A bond is formedbetween the first core portion foam core and the layer of resinpreimpregnated tape. Also, the epoxy, microspheres, the other materialsof the second core portion bond to each other and also bond to thecarbon fiber tape in the mold. Moreover, the first core portion and thesecond core portion materials are bonded together by the cross-linkingof the epoxy.

The mold is cooled and the formed blade is removed from the mold. Themold is then cooled and the formed structure is removed from the mold.

In one embodiment, “Expancell” microspheres are used to form the secondcore portion. In the formation of these microspheres, a drop of ahydrocarbon, liquid isobutene, is encapsulated in a gasproof, polymericthermoplastic shell. When this microsphere is exposed to heat, the shellsoftens and the hydrocarbon inside the shell increases its pressure,expanding the shell. Before expansion, the diameter of the microsphereis typically 10-12 um and the density is 1000-1200 kg/m3. Afterexpansion, the diameter of the microsphere is 40-50 um and the densitydecreases to 20-30 kg/m3.

The temperature at which expansion starts as well as the temperature atwhich the maximum expansion and the lowest density is obtained dependson a variety of factors including the rate of heating of the shells. Attemperatures above the temperature at which the highest expansion isobtained the microspheres gradually collapse.

The microspheres are highly resilient. The expanded microspheres areeasy to compress. Due to this resiliency, the microspheres can withstandcycles of loading/unloading without collapsing or breaking. Thisproperty is important for use in shock absorbent materials, such as ahockey blade.

Thermoplastic microspheres are distinct from glass microballoons. Glassmicroballoons are heavier than thermoplastic microballoons.Additionally, glass microballoons do not exhibit the same dampeningproperties as thermoplastic microballoons. For these reasons, althoughglass microballoons could be used, thermoplastic microspheres arepreferred over glass microballoons in the manufacture of hockey stickblades, which must be lightweight, flexible and capable of withstandingconsiderable forces.

As a first step in one embodiment of the process, a group of expandablemicrospheres are heated until they expand from their original size to anexpanded size. The expanded microspheres have a diameter of 60-120 um.

The expanded microspheres are then mixed with unexpanded microspheres.This combination of expanded and unexpanded microspheres is mixed withan epoxy material, such as Epon828. Other strengthening materials, suchas aramid pulp, chopped fiber glass or chopped carbon fiber can also beadded to the mixture. Carbon nanotubes can also be added enhancestiffness and shear strength. A curing agent is also added to themixture. The final epoxy mixture 620 has the consistency of modelingclay, as shown in FIG. 6.

The mixture of the expanded microspheres, the unexpanded microspheres,the epoxy, the other strengthening materials and the curing agent isthen formed in the shape of the second core portion.

The unexpanded microspheres are required to produce enough pressure onthe outer walls of the structure. Without sufficient pressure during themolding process, the walls will be wrinkled and/or have large numbers ofvoids and/or other imperfections. The expanded microspheres increase theviscosity of the material, making a more stable preform during thekitting operation. Also, the expanded microspheres allow for a largervolume preform, which is closer to the final geometry of the part. Thisis advantageous because it allows less movement (and more precision) ofthe structural fibers during the molding process.

The combination of expanded and unexpanded (or partially expanded) isimportant because it provides a high viscosity material which producesenough pressure to compress/consolidate the carbon fibers walls aroundit.

In one embodiment, the core comprises the following materials(parts/weight):

Base epoxy (Epon 828): 100Chopped fiber, e.g., Aramid Pulp 3091 (from Teijin): 2.5Hardener (curing agent): 14.82Expancel (pre-expanded) 092DET80d20: 2Expancel (unexpanded) 051DU40: 2.5

In another embodiment, a group of expandable microspheres are heated andthey partially expand from their original size to a larger size, but notto their full size. The partially expanded microspheres have a diameterof 60-90 um.

The partially expanded microspheres are then mixed with unexpandedmicrospheres. This combination of partially expanded and unexpandedmicrospheres is mixed with an epoxy material, such as Epon828. Otherstrengthening materials, such as aramid pulp, chopped fiber glass orchopped carbon fiber are also added to the mixture. Carbon nanotubes canalso be added enhance stiffness and shear strength. A curing agent isalso added to the mixture. The final epoxy mixture also has theconsistency of modeling clay.

The mixture of the partially expanded microspheres, the unexpandedmicrospheres, the epoxy, the other strengthening materials and thecuring agent is then formed in the shape of the second preform asdescribed above.

In alternative embodiments, different combinations of core materials areused to create distinct recipes of core mixtures. The different mixturescan be used to create a blade with zones of varying density andstiffness. The bottom of the blade and the heel of the blade aretypically subject to the most force and impact from striking the ice ora hockey puck. Core mixtures with higher density materials can be placedin the areas of the blade subject to greater forces and impacts, such asthe bottom or heel, to create stronger blade regions.

The reader should understand that these specific examples are set forthmerely to illustrate examples of the invention, and they should not beconstrued as limiting the invention. Many variations in the connectionsystem may be made from the specific structures described above withoutdeparting from this invention.

While the invention has been described in detail in terms of specificexamples including presently preferred modes of carrying out theinvention, those skilled in the art will appreciate that there arenumerous variations and permutations of the above described systems andmethods. Thus, the spirit and scope of the invention should be construedbroadly as set forth in the appended claims.

We claim:
 1. A method comprising: sizing a foam core to form a firstcore portion; providing an epoxy mixture to form a second core portion;placing the first core portion and the second core portion into apreform; heating the preform so as to cause the epoxy mixture to flowinto the shape of the preform and around the first core portion;wrapping the first core portion and the second core portion with fibertape to create a wrapped preform; stitching the first core portion witha thread, the thread extending between a first wrapped face and a secondwrapped face of the wrapped preform; placing the wrapped preform in amold; heating the mold to bond the first core portion and the secondcore portion; cooling the mold; and removing the formed structure fromthe mold.
 2. The method according to claim 1 further comprising curvingthe first core portion prior to placing the first core portion into thepreform.
 3. The method according to claim 2 wherein the first coreportion and the second core portion are wrapped with a layer carbonfiber.
 4. The method according to claim 3 wherein the layer of carbonfiber comprises a first sheet and a second sheet and wherein the firstcore portion and the second core portion are placed on the first sheetand wherein the first sheet is wrapped around portions of the first coreportion and the second core portion and wherein the second sheet isplaced over the first core portion and the second core portion prior toplacing the first core portion and the second core portion into thepreform.
 5. The method according to claim 1 wherein the second coreportion mixture further comprises a plurality of expanded and partiallyexpanded microspheres and wherein when the mold is heated the partiallyexpanded microspheres fully expand.
 6. The method according to claim 1wherein the second core portion mixture further comprises a plurality ofexpanded and unexpanded microspheres and wherein when the mold is heatedthe unexpanded microspheres fully expand.
 7. The method according toclaim 1 further comprising the step of, after wrapping the foam corewith a layer of fiber tape, placing a non-tacky veil on at least aportion of the first core portion.
 8. A blade comprising: a first coreportion formed of foam; a second core portion comprising an epoxy havinga plurality of expanded microspheres; the first core portion and thesecond core portion forming a core comprising a first core face and asecond core face; a layer of carbon fiber wrapped around the core; alayer of resin preimpregnated tape wrapped continuously around at leastthe first core face and the second core face; a thread stitched on thepreimpregnated tape on the first core portion.
 9. The blade as in claim8 wherein the first core portion and the second core portion are bondedto form a continuous core.
 10. The blade as in claim 9 wherein the firstcore portion has a bottom surface which is bonded to a top surface ofthe second core portion by cross-linking the epoxy.
 11. The blade as inclaim 8 further comprising a non adhesive scrim applied to the portionsof the resin preimpregnated tape that extend along the first coreportion.
 12. The blade as in claim 8 wherein the first core portion hasan oval-shaped end.
 13. The blade as in claim 8 wherein the second coreportion has an oval-shaped end.
 14. The blade as in claim 1 wherein anend of the first core portion or the second core portion has a hookshape.
 15. The blade as in claim 8 wherein the core forms part of ahockey blade comprising a toe region and a heel.
 16. The blade as inclaim 15 wherein the first core portion extends from the heel of theblade to the toe region of the blade.
 17. The blade as in claim 15wherein the second core portion extends from the toe region of the bladeto the heel of the blade.
 18. The blade as in claim 16 wherein the firstcore portion is thickest at the heel portion of the blade and tapersfrom the heel of the blade to the toe region of the blade.
 19. The bladeas in claim 17 wherein the second core portion is thickest at the toeregion of the blade and tapers from the toe region of the blade to theheel of the blade.
 20. The blade as in claim 8 wherein the first core isof a lower density than second core portion.